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Piatã

-13.152° S   41.773° W  ·  1282 M
35 /100
PEAK
Marginal, but there is a 1 hour gap from 20:00.
BEST WINDOW 20:00–21:00 · ASTRO DARK 19:00–05:00 · MOON 0%
Transparency
0.35
Seeing
0.71
Cloud
48%
Moon
0%

Fair tonight

Hour by hour, local to Piatã. Colour encodes the score and nothing else; every other measurement is luminance.

Sky state
Lighter = daylight and twilight  ·  unshaded = astronomical dark
Score
18
19
20
21
22
23
00
01
02
03
04
05
06
0
23
35
8
0
7
3
0
2
1
1
0
0
BEST WINDOW
Low cloud
51%
66%
48%
86%
99%
88%
95%
100%
96%
98%
98%
100%
100%
Mid cloud
7%
2%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
High cloud
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
Transparency
0.42
0.35
0.33
0.10
0.10
0.22
0.19
0.20
0.21
0.22
0.22
0.21
0.21
Seeing
0.68
0.69
0.68
0.69
0.67
0.63
0.59
0.62
0.66
0.68
0.70
0.71
0.72
Moon clear
down
down
down
down
down
down
down
down
down
down
down
down
down
Inspect

Cloud tracks show clear sky — a longer bar is better. The figure inside each track is the raw measurement.

Why this hour scored what it did
18 Clouded out · 0/100
Starting from
100
Cloud
−54
Transparency
−11
Seeing
−3
Moonlight
−0
Darkness
−33
Score
0
CLOUD 51% LOW 51% MID 7% HIGH 0% SUN -5.1° MOON -1.3° / 0% WIND 5 TEMP 18°
Excellent 75+ Good 55+ Fair 35+ Poor 15+ Not worth it Seeing is estimated from surface wind — see how we score.

What are you doing tonight?

The same forecast, weighted for the target. Planetary work barely cares about moonlight; long exposures die on high cloud a visual observer would never notice.

SET UP 19:30 · OBSERVE 20:00–21:00 · 1H · MEAN 37

Darkness and moonlight dominate. Faint fuzzies need a genuinely dark sky more than they need steady air.

18202200020406
CLOUD BREAKS 20:00CLOUD RETURNS 21:00
SET UP 19:30 · OBSERVE 20:00–21:00 · 1H · MEAN 38

Seeing is everything and moonlight is irrelevant. Bright targets punch through twilight, so darkness barely counts.

18202200020406
CLOUD BREAKS 20:00CLOUD RETURNS 21:00MOONLIGHT IGNORED FOR THIS TARGET
SET UP 19:30 · OBSERVE 20:00–21:00 · 1H · MEAN 35

Tolerates soft seeing, but high cloud wrecks a wide frame and moonlight raises the background everywhere.

18202200020406
CLOUD BREAKS 20:00CLOUD RETURNS 21:00
NO USABLE WINDOW FOR THIS TARGET TONIGHT

Needs conditions to hold still for hours. Sustained transparency matters more than any single good hour.

18202200020406
CLOUD NEVER DROPS BELOW 48%
SET UP 19:30 · OBSERVE 20:00–21:00 · 1H · MEAN 36

Naked eye, whole sky. Total cloud and moonlight are the only things that count.

18202200020406
CLOUD BREAKS 20:00CLOUD RETURNS 21:00
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The next week of nights

Tonight · 12 Aug
35
Fair
MOON 0%
20:00–21:00
Tomorrow · 13 Aug
82
Excellent
MOON 3%
19:00–05:00
Friday · 14 Aug
81
Excellent
MOON 7%
19:00–04:00
Saturday · 15 Aug
87
Excellent
MOON 15%
21:00–22:00
Sunday · 16 Aug
85
Excellent
MOON 23%
21:00–22:00
Monday · 17 Aug
12
Clouded out
MOON 32%
Tuesday · 18 Aug
52
Fair
MOON 42%
21:00–22:00
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Nearby locations

About this forecast

Conditions for Piatã, Brazil are computed from the MET Norway forecast model for these exact coordinates, combined with sun and moon positions we calculate directly. The score weighs cloud cover by layer, atmospheric transparency, estimated seeing, moonlight and how dark the sky actually gets. Read the full method →